How to find the Oxidation Number for Mn in MnO2

To find the correct oxidation number for MnO2 (Manganese (IV) oxide), and each element in the compound, we use a few rules and some simple math.

First, since the MnO2 doesn’t have an overall charge (like NO3- or H3O+) we could say that the total of the oxidation numbers for MnO2 will be zero since it is a neutral compound.

We write the oxidation number (O.N.) for elements that we know and use these to figure out oxidation number for Mn.

----------
GENERAL RULES
In a netural compound all O.N. must add up to zero.
Group 1 = +1
Group 2 = +2
Hydrogen with Non-Metals = +1
Hydrogen with Metals (or Boron) = -1
Fluorine = -1
Oxygen = -2 (except in H2O2 or with Fluorine)
Group 17(7A) = -1 except with Oxygen and other halogens lower in the group
----------
We know that Oxygen usually is -2 with a few exceptions. When Oxygen is in a peroxide, like H2O2 (Hydrogen peroxide), it has a charge of -1. When it is bonded to Fluorine (F) it has an oxidation number of +2.

Here it is bonded to element symbol so the oxidation number on Oxygen is -2. Using this information we can figure out the oxidation number for the element Mn in MnO2.

[ohbianca]

Sir you just taught me this perfectly. It’s so easy to understand in this video I don’t know how I didn’t understand this in class. Thanks so much !!

[loi]

Thank you so much Dr. B! Your video made it so easy for me to understand this problem.

[ysona]

Your video are always of great help .. you made the way of explanation so easy .
I often come to this channel whenever a doubt occurs...Thanks for putting effort for us

[ranalia]

Hey! Thanks for all these explanations, your channel is my first adress for chemistry's fascinating world!
I have a question here and I don't know how to define oxygen's oxidation number. For instant Mn can have several numbers like +2, +3, +4, +6, +7. And we know that this situation applies to oxygen, like it can have -2, -1, -1/2, 0, +2. In this molecule we name it Manganese(IV) oxyde, but couldn't it be Manganese(
II) peroxide ? Or the oxygen takes -1 only with metal ions?

[chaitalibiswas]

Thank you a lot 😊😊😊
I don't know how I didn't understand it earlier

[xrmah]

Appreciate your work♥️
Easy to understand

[shellyrana]

Thank you so much. It is really beneficial .

[megandavis]

Can anyone help explain to me why O2 remains having an oxidation number of -2 and not -4? I understand how to get the +4 for Mn and that the sum = 0 but wouldn't that assign a -4 to O2, not a -2?

[ammaarahadjiet]

Is the Oxidation number for O2 not going to be -1? Because it is a peroxide? Or is my understanding of peroxide incorrect...

[Wuzzapy]

But in peroxides, oxygen counts as -1, right?

[pedrodavid]

Lo he entendido perfectamente y eso que no entiendo mucho el inglés